Portable testing set for measuring line induction



Jun 12. 192a 1,673,422

C. T. REISZ PORTABLE TESTING SET FOR MEASURING LINE INDUCTION Filed May 22, 1926 G d 72 Ground alto: new A Patented June 12, 1928. y

UNITED STATES CHARLES T. REISZ, OF CHICAGO, ILLINOIS,

GRAPH COMPANY, OF CHICAGO, I LL I nssreivon 'ro wnsrnnn union TELE- nors, a coaronarron or rumors.

PORTABLE rnsrine sn'r non mnnsunrne LINE innucrron.

Application filed May '22,

My invention, in its broad aspect, relates to a method of, and apparatus for,measuring and analyzing alternating currents. Specifically, it concerns testing apparatus for investigating the induction of power systems.

It is the object of this invention to provide apracticable circuit for measuring alternating current inductive disturbances at a point in the line conductor remote from the point at which the disturbance originates.

It is a feature of my invention that in analyzing and measuring the alternating current in the line conductor, a coil and a condenser are provided and adjusted to resonance with the current to be measured and that the resonance current is then rectified prior to its application to the measuring instrument. i

The test set of my invention avoids the drawbacks of previously known systems for measuring inductive disturbances, such as the taking of readings from an indicating meter,-a procedure which is subject to the personal element and becomes monotonous for the reader when extended over long periods.

My inventi on provides means for calibratingthe direct currentrecording meter, either with alternating current, which may be of the same frequency as the induction to be tested, or with direct current.

Other advantages of the method and apparatus of my invention will be apparent from the following description by reference to'the annexed drawing, which showsja prer ferred form of the invention wherein:

L represents the terminal of a line conductor subject to the powervinduction which is to be investigated. The line conductor may be any conductor within the field of. influence of the powerline the inductive effect of which it is desired to investigate. It may be a special test conductor or it may I be a conductor normally used for telegraphic or other purposes. G represents the termi nal of a ground connection. These terminals may be any convenient means, such as jacks, by which connection may be made to line and to ground.

A direct current recording meter RM, is connected in'the diagonal of a double rectifier made in the form of a balanced bridge, the arms of which include respectively, fresistances 1', and'r and crystals (3, the latter 1926. Serial No. 111,041.

connected in the arms in opposite directions, as shown. Th1s arrangement is connected in series with 'a resonant path including a coil and a condenser made variable for purposes of tuning. In order to provide for an adjustment of the magnitude of the current, regulatingresistances R andR are connected, the former in series, and the latter in shunt, with the combination of double rectifier and tuning impedance.

, For purposes of calibration, the circuit of the test set includes apparatus formeasuring the'resistance of the line conductor external to the set. This includes a reversing switch sat for connecting battery B between line and ground, by way, if desired, of the previously mentioned terminals L and G.

l A voltmeter V connected across the line, and

a direct current milliammeter MA connected 1n series in the llne give readmgs from'which the resistance of the line may be calculated by the IR dr'opl; i I

Actual calibration is accomplished by certain other apparatus adapted for connection across the terminals L, G of the measuring circuit. This additional apparatus is made up of a potentiometer P connected to the source of test current S, a milliammeter MA and series resistance 9",, connected between the output'terminals of'the potentiometer, and a resistance B connected between line and potentiometer, and equal in magnitude to the calculated, or otherwise predetermined, resistance of the line. i

W here alternating current isnot available 'for calibration, direct currentinay be used. In this case,",1t 1s necessary to replace] the tuning impedance by a resistance which corresponds to the effective resistance of the coil at the frequency to be tested. The use of alternating current for calibr however, preferred. p

' The method of operation of the system in measuring the induction will be apparent from the following: i

The resistance of the line conductor exter nal to the testing set is determined by connecting the meter audits associated circuits to line 'and ground, through terminals L and G. In order to eliminate anyconstant ation is, i

earth potential effects, readings are taken a with the reversing switch in both positions. After calculation of the resistance from the voltmeter and milliammeter readings, the resistance R at the calculated value,

evident that the crystals operate, each one as a shunt about its corresponding resistance, during alternate half Waves of the alternat: ing current. Accordingly, currentpulses of afrequency equal to twice the frequency of alternation of the current to be measured, will be transmitted"through the direct-cur- .reut recording meter, always in the same direction. I s

The shunt. and series, resistances are adjusted ,for the magnitude of the induction,

' and calibratingisgperformed between, altery to 'nating current milliammeter MA I and the recording; meter RM, using the previously determined resistancefof the line tocompensate for the drop in voltage over the circuit to be tested After jcalibi'ati0n, j the test source S is disconnected fromthe recording meterand ts assoclatfed apparatusby opening the twoswitches shown connected to the outer terminals of resistances R and 1 The line conductor is then connected to the line jack" and the, ground to ground jack, at

L and G, respectively, whereupon alternating current derived in the line conductor by inductionfrom a. neighboring .power ,line is caus'edto pass through the test set. If necessary, readjustment i of the variable tuning element, as condenser F, is made until the line conductor; is in resonance with the induced alternating current. This is evidenced, as before, by amaximum reading on the recording meter RM, Since the meterhas already,ibyiconnectionto test source S, been calibrated, in terms of power induction units if desired, it is obvious that. the reading of the meterwill give a direct measurement of tlie,;power induction in the line, conductor.

Where calibration is performed with direct current, instead of alternating current, the r'esistancej-R is connected to the double reetifier, ,H and F being. temporarily removed from circuit. 1 Calibration is] made onboth polarities and the results averaged.

.lVhen calibrationis complete, resistance isv disconnected," and; the tunin .put into the, circuit and tunedl'neasurin the induction. 1 ,It is O. V o s .thatwarious modifications.

while actually may be made in the method and apparatus impedance ,is.

of my inventidn without departing from the spirit of the invention. Accordingly, I do not limit myself to the precise arrangement disclosed,- but claim as my invention all ni rangements coming within the scope of the annexed claims.

' at I claim" is:

1. In apparatus for investigating the alternating current induction in a line conductor, a test set adapted to be connected in series with said line conductor comprising means for tuning said lineconductor to resonance with the current to be measured, and means for reetifyingsaid current. l

2. Inapparatus for measuring alternating current induction in a line conductor, a test set comprising a coil and a condenser adjust- I able totune the line conductor to resonance with the current to be measured, and means for I rectifying and, measuring bot-h half- Waves of said alternating current.

3. In apparatus for investigating the in duction in a line conductor, the combination of an indicating instrument, a source of test a current, impedanceelements includinga coil and acondenser wlth means to vary one of said elements for tuning, and means to eonnect said test current source and said line conductor alternately to, said indicatinginstrumentthrough one or more of said impedance elements. h l 4. Themethod of measuring alternatin current inductionin a lineconductor whic comprises augmenting the induction currents by establishing a condition of electrical resonance therefor, and measuring the uugmented, current.

5. The method of comprises varying the amplitude of the induction until it.attains a maximum, rectifying the varied current and measuring the rectified current. 11

. 6. In a system for measuring alternating current in allneconductor, means to'tune the line to the frequency ofthe alternating current; a direct 7 current measuring. instrument and a rectifying means, and in combination therewith, calibrating means for ing means a y i 7. In a system for measuring alternating "current in a line conductor, means to tune theline to the frequency of the alternating current, a directcurrent measuring instrument and a rectifylng means, and in combination therewith, cahbrating-means'for the measuring instrument comprising a, source "of. alternating test current, "an artificial line corresponding in impedance to the line conductorg and means to connect said testjcur rent source to said measuring instrument measuring alternatin current induction in a line conductor whic through said artificial line, said rectifying and said tuning means.

8. In a system for investigating the induction originating at a distant point in a line conductor, the combination of means for determining the normal impedance of the line conductor, means for tuning the line conductor to obtain a minimum impedance at the induction frequency, a rectifying circuit, a direct current measuring instrument connected to said rectifying circuit, and a calibrating circuit through said tuning means, said rectifying circuit and said measuring instrument comprising a sourceof test current of the induction frequency and an artificial line adjustable to the value of the normal line impedance.

9. In a system for measuring power induction in a line conductor, the combination of a direct current measuring instrument, a rectifying circuit to the direct current terminals of which said instrument is connected,

a path connected to said rectifier circuit comprising impedance elements adjustable to resonance at the induction frequency, and,

double rectifier to the direct current terminals of which said instrument is connected,

a means between the line conductor and the rectifier comprising an inductance c011 and a condenser adjustable to tune the line conductor to resonance at the induction frequency, means for passing an alternating test current through said tuning means and said rectifier, and means for calibrating said instrument by means of said test current;

In testimony whereof I afiix my signature.

CHARLES T. REISZ, 

